Remove -t flag

Now that the hardcoded protocols have been removed, users should
provide their own protocol file to interpret protocol. So we'll
assume that user want wayland-tracer to interpret protocol as long
as they provide protocol definition. So the -t flag is unneeded.
Avoid a possible null pointer dereference

If the user didn't provide wayland core protocol, the program would
crash because of a null pointer dereference. Fix that.
make lookup_type a public function

Rename it to tracer_analyzer_lookup_type to use it in tracer.c
Use interface lookup provided in tracer-analyzer.c